Ultracapacitors are of interest as primary electrical energy storage devices for vehicles and other functions. In such applications it is important to be able to anticipate the remaining useful life of the ultracapacitor energy storage device. FIG. 1 shows plot 10 of the instantaneous projected life Y(T,V) of an ultracapacitor cell as a function of the cell voltage V for different cell temperatures T, where line 11 corresponds to 15 degrees Celsius, line 12 to 25 degrees Celsius, line 13 to 35 degrees Celsius, line 14 to 45 degrees Celsius, line 15 to 55 degrees Celsius, and line 16 to 65 degrees Celsius, respectively. Lines 11–16 of plot 10 can be expressed as:Y(V,T)=10(aT+bV+c)  [1]where a, b, and c are constants. When Y(T,V) is expressed in years, V in volts and T in degrees Celsius, then a=−0.03333333, and b=−3.33333333 and c=10.1666666666 are useful values. While the above expression is useful in providing a snapshot of projected lifespan for a variety of specific cell conditions, it does not reflect a projected life based on the cumulative effects of history of operation, nor present time varying cell conditions. Further, neither FIG. 1, nor the expression it represents, define the method for forecasting the remaining operating life of an ultracapacitor at any current intermediate point in its lifespan. Thus a need continues to exist for an improved means and method for forecasting the remaining life of an ultracapacitor power source, especially as a power source for vehicles.
Accordingly, it is desirable to provide an improved means and method for determining the projected lifespan of an ultracapacitor power source, especially for ultracapacitor types useful for vehicle propulsion. In addition, it is desirable that the means and method be automatic, not requiring any participation by the vehicle user. Still further it is desirable that the system and method of the present information store information on past vehicle operating conditions so that the cumulative impact thereof can be evaluated. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.